Proton solvation in the sulfuric acid-water-1,4-dioxane system

The dependence of the optical density on the composition of the solution in the range of 0–60%, 1,4-dioxane in 10% aqueous solution of H₂SO₄ was obtained by FMIR IR spectroscopy. It was shown that in the solutions studied, the proton is in the form of the two simplest stable solvates: H₅O₂ ⁺ and H₂OHD⁺ ions, where D is the 1,4-dioxane molecule. The equilibrium concentrations of the proton solvates were estimated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 298–301, February, 1990.     

Acidity function of methanesulfonic acid solutions in ethyl acetate

The acidity function of solutions of methanesulfonic acid (MSA) in ethyl acetate (EA) was measured by the indicator method at 25 °C in the 0.4—100% concentration range. Molecular complexes formed by MSA and EA show a higher ionizing activity than H₅O₂ ⁺ ions. The relative ionizing activity of the MSA·EA complexes and ion pairs formed by MSA and DMF was determined.     

Diffusion with hydrolysis and ion association in aqueous solutions of beryllium sulfate

Taylor dispersion is used to measure mutual diffusion coefficients for aqueous solutions of beryllium sulfate at concentrations from 0.005 to 1 mol-L^–1 at 25°C. Least-squares analysis of the dispersion profiles shows that diffusion of the partially hydrolyzed salt produces a small additional flow of sulfuric acid, about 0.04 mol sulfuric acid per mole of total beryllium sulfate. Ternary diffusion coefficients measured for the aqueous BeSO₄–H₂SO₄ system are qualitatively consistent with Nernst-Planck predictions based on the formation of beryllium sulfate ion pairs, bisulfate ions, and the hydrolysis equilibria 2Be²⁺+H₂O= Be₂OH³⁺+H⁺, 3Be²⁺+2H₂O=Be₃(OH) ₂ ⁴⁺ +2H⁺. Except for very dilute solutions, the predicted flow of sulfuric acid is small compared to the flow of beryllium sulfate because most of the beryllium ions are protected from hydrolysis by the formation of BeSO₄ ion pairs, and most of the hydrogen ions produced by hydrolysis are converted to less-mobile bisulfate ions.     

Acid Catalysis in Reaction of Ozone with Chloride Ions

The kinetics of the interaction of ozone with aqueous solutions of chlorides resulting in Cl₂ evolution to the gas phase was studied. The reaction of O₃ with Cl^– is accelerated by H⁺ ions. The effects of the concentrations of H⁺ and Cl^–, the ionic strength, and temperature (ranged from 7 to 60°C) on the reaction rate were studied. A mechanism explaining the experimental kinetics was proposed. The acid catalysis is due to the formation of the HO₃Cl complex, which is in equilibrium with H⁺, O₃, and Cl^–. The constants of reactions involved in the proposed mechanism were determined.     

Characteristics of the complexing of chitosan with sodium dodecyl sulfate,according to IR spectroscopy data and quantum-chemical calculations

The complexing of protonated chitosan with dodecyl sulfate ions in water solutions is studied using IR spectroscopy data and quantum-chemical calculations. It is established that the electrostatic interaction between the protonated amino groups of chitosan and dodecyl sulfate ions is apparent in the IR spectrum as a band at 833 cm^?1. The need to consider the effect the solvent has on the formation of hydrogen-bound ion pairs [CTS⁺ ? C₁₂H₂₅O₃^-] is shown via a quantum-chemical simulation of the equilibrium geometry and the energy characteristics of complexing and hydration.     

Precipitation of Bismuth(III) Tartrates from Nitrate Solutions

The precipitation of bismuth(III) from nitrate solutions on addition of aqueous solutions of tartaric acid and sodium tartrate was studied by X-ray phase analysis, thermogravimetry, IR spectroscopy, and chemical analysis. Conditions for the formation of [Bi(NO₃)(H₂O)₃]C₄H₄O₆ and [Bi(C₄H₄O₆)(C₄H₅O₆)] · 3H₂O were determined.     

Ion pairs and the strength of hydrofluoric acid

The available spectroscopic data do not support the current theory on the nature of aqueous hydrofluoric acid: namely, undissociated HF molecules in dilute solutions (weak acid), and HF^?₂ or more complex ions at higher concentrations (strong acid). A different model is proposed, involving as a dominant species ion pairs of hydorxonium fluoride H₃O⁺…F^?linked by an exceptionally strong hydrogen bond. This model is also more consistent with various other properties of the H₂O-HF system.     

Synthesis and physicochemical study of the PMo<Subscript>11</Subscript>(TiO)O<Stack><Subscript>39</Subscript><Superscript>5−</Superscript></Stack> heteropolyanion

Procedures were developed for the synthesis of the guanidinium (Gua) and tetrabutylammonium (TBA) salts of 11-molybdotitano(IV)phosphate heteropolyanion (MTPH) from solutions with the stoichiometric ratio P: Mo = 1: 11 and in excess of titanium(IV) ions, Ti: P ≥ 1.5, at pH 1.85–1.90. MTPH was isolated as the (Gua)₅PMo₁₁(TiO)O₃₉ and (TBA)₅PMo₁₁(TiO)O₃₉ salts. The composition and formula of MTPH were established by chemical analysis, electronic absorption spectroscopy in the visible region of the oxidized and reduced MTPH forms, IR spectroscopy, and ³¹P NMR. H₅PMo₁₁(TiO)O₃₉, obtained by ion exchange of the Gua salt in an aqueous-organic medium, is a strong pentabasic acid. MTPH reacts with H₂O₂ to form a peroxo complex with limited stability in an aqueous solution. In aqueous-organic media, the peroxo complex is more stable. In acetonitrile, MTPH persists for several days.     

Advancing understanding of actinide(iii) (Ac,Am, Cm) aqueous complexation chemistry

The positive impact of having access to well-defined starting materials for applied actinide technologies – and for technologies based on other elements – cannot be overstated. Of numerous relevant 5f-element starting materials, those in complexing aqueous media find widespread use. Consider acetic acid/acetate buffered solutions as an example. These solutions provide entry into diverse technologies, from small-scale production of actinide metal to preparing radiolabeled chelates for medical applications. However, like so many aqueous solutions that contain actinides and complexing agents, 5f-element speciation in acetic acid/acetate cocktails is poorly defined. Herein, we address this problem and characterize Ac³⁺ and Cm³⁺ speciation as a function of increasing acetic acid/acetate concentrations (0.1 to 15 M, pH = 5.5). Results obtained via X-ray absorption and optical spectroscopy show the aquo ion dominated in dilute acetic acid/acetate solutions (0.1 M). Increasing acetic acid/acetate concentrations to 15 M increased complexation and revealed divergent reactivity between early and late actinides. A neutral Ac(H₂O)₆₍₁₎(O₂CMe)₃₍₁₎ compound was the major species in solution for the large Ac³⁺. In contrast, smaller Cm³⁺ preferred forming an anion. There were approximately four bound O₂CMe¹⁻ ligands and one to two inner sphere H₂O ligands. The conclusion that increasing acetic acid/acetate concentrations increased acetate complexation was corroborated by characterizing (NH₄)₂M(O₂CMe)₅ (M = Eu³⁺, Am³⁺ and Cm³⁺) using single crystal X-ray diffraction and optical spectroscopy (absorption, emission, excitation, and excited state lifetime measurements).

Actinide complexation from aqueous acetic acid/acetate buffered solutions is described. The number of water ligands was directly correlated with the acetate concentration and characterized by X-ray absorption and optical spectroscopy.     

Reactions of hydrogen peroxide with acetylacetone and 2-acetylcyclopentanone

A reaction of acetylacetone with equimolar amount of concentrated aqueous H₂O₂ in both organic solvents (Bu^tOH, AcOH) and water at various temperatures gave the corresponding 3,5-dihydroxy-1,2-dioxolanes with different configuration of stereogenic centers. In the presence of an excess of H₂O₂, 3,5-dihydroxy-1,2-dioxolanes were converted to a mixture of 5-hydroperoxy-3-hydroxy-1,2-dioxolanes and further to a mixture of dimeric 1,2-dioxolan-3-ylperoxides. All the peroxides formed exist in solutions as equilibrium mixtures with the starting reagents. A prolonged reflux of solutions of 3,5-dihydroxy-1,2-dioxolanes in Bu^tOH in the presence of a large excess of H₂O₂ led to the skeletal rearrangements of the substrates to a mixture of propionic acid and hydroxyacetone, which underwent further oxidative transformations. Unlike acetylacetone, 2-acetylcyclopentanone reacted with H₂O₂ in aqueous phase or in solutions in Bu^tOH under thermodynamic or kinetic control with the formation of the corresponding 5-hydroperoxy-3-hydroxy-1,2-dioxolanes, rather than 3,5-dihydroxy-1,2-dioxolanes. Thermodynamically controlled process in solution in AcOH gave a mixture of all four possible hydroperoxyhydroxy-1,2-dioxolanes. These cyclic peroxides in solutions in ButOH or AcOH readily converted to a mixture of AcOH, glutaric, α-methyladipic, and α-hydroxy-α-methyladipic acids. An active α-hydroxylation of the substrate was observed upon reflux of a solution of 2-acetylcyclopentanone and H₂O₂ in AcOH.     

Acidity function of methanesulfonic acid solutions in DMF

The acidity function of solutions of methanesulfonic acids (MSA) in DMF and H₂O were measured by the indicator method at 25 °C in the 0–100% concentration range. A higher ionizing activity of HCl complexes with DMF as compared to that of similar MSA complexes was established. The relative ionizing activity of MSA molecules, H₅O₂ ⁺ ions, and ion pairs between MSA and DMF was determined. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 1940–1943, October, 1999.     

H+ and OH− ions in aqueous solutions vibrational spectra of hydrates

The ions (H₂O ... H ... OH₂)⁺ and (HO ... H ... OH)^? are the simplest stable H⁺ and OH^? hydrates in aqueous acid and base solutions, respectively. Using the attenuated total reflection method, the IR spectra of aqueous HCl and KOH solutions are obtained and the assignment of the H₅O₂⁺ and H₃O₂^? vibrational frequencies is performed. The absorption spectrum of the OHO fragment is separated from the spectra of the solutions investigated. This spectrum exhibits a broad continuous band and two rather narrow bands at its background which are assigned to the antisymmetrical stretching vibration and to the bending vibrations of the fragment. A theoretical model is suggested which explains the origin of the continuum by a strong proton-phonon coupling. The model takes into account the large number of low-frequency vibrational modes of the system; the frequency dispersion for these modes is assumed to be sufficiently large. The continuous absorption bandshape is calculated in the Condon approximation. The theoretical absorption curve is in good agreement with experiment at reasonable values of the parameters involved.     

Three organic–inorganic hybrid B-Anderson polyoxoanions as building blocks: syntheses,structures, and characterization of [(C6H5NO2)2Ln(H2O)6](CrMo6O24H6)·2C6H5NO2·6H2O (Ln = Sm,Dy, Er)

Three new B-Anderson type polyoxometalates, [(C₆H₅NO₂)₂Ln(H₂O)₆](CrMo₆O₂₄H₆)·2C₆H₅NO₂·6H₂O (Ln?=?Sm 1, Dy 2 and Er 3), have been synthesized in aqueous solution and structurally characterized by single-crystal X-ray diffraction, IR spectra, UV spectroscopy, and fluorescence spectroscopy. Crystal structure analysis reveals that these three compounds have the same composition and are isostructural, assembled by B-Anderson type polyoxoanion [CrMo₆O₂₄H₆]^3?, rare-earth ions, and ligands. UV spectroscopy shows that 1 is stable when pH is 4.50–5.83. The fluorescence spectra of 2 indicate that both rare-earth ions Dy³⁺ and pyridine-4-carboxylic acid ligands function in the charge transition of the compound.     

Chemical processes on active carbon surface: A new example of nitrogen fixation

The behavior of activated carbon fibers (ACF) and activated carbon (AC) in water and aqueous solutions of H₂O₂, NaOH, NaCN and KI₃ in the presence of atmospheric air is studied by physicochemical methods: X-ray photoelectron spectroscopy (XPS), ESR, and attenuated total reflectance IR (ATR-IR) and Fourier Transform IR (FT-IR) spectroscopy. The superoxide radical anion O ₂ ^?· is shown to exist on the ACF surface in aqueous solutions, whose formation is explained by reaction of molecular oxygen with radical active centers of surface defects. It is found that in aqueous solutions of inorganic compounds, both possessing (H₂O₂, KI₃) and not possessing (NaOH, NaCN) pronounced oxidative properties, the ACF surface is oxidized more rapidly than on aging in air. Evidence for fixation of atmospheric nitrogen on contact of ACF and AC with H₂O or aqueous solutions of NaOH, NaCN, and KI₃ is obtained. Possible conjugate redox reactions resulting in fixation of N₂ molecules and oxidation of the surface of carbon materials are discussed.     

Electron beam induced degradation of clopyralid in aqueous solutions

The degradation characteristics of clopyralid irradiated by electron beam (EB) was studied in aqueous solutions. The effects of factors, such as initial clopyralid concentrations, addition of radicals scavenger, initial solution pH and addition of H₂O₂, were investigated on clopyralid degradation efficiency and mechanism. It was found that the EB-radiolysis was an effective way to degrade clopyralid and its degradation rate decreased with the increasing of substrate concentration. In the investigated initial concentrations range of 100?C400 mg L^?1, the radiolytic degradation of clopyralid followed a pseudo-first kinetic order. The results from addition of radicals scavenger indicated that both ^?OH and e _aq ^? played significant roles in the degradation of clopyralid. Furthermore, the alkaline condition and addition of H₂O₂ (<10 mM) in the solution also slightly enhanced the efficiency of clopyralid degradation. The ion chromatography analysis showed that some organic acids (formic acid, acetic acid and oxalic acid) were formed, while the completely dechlorination of the substrate was achieved and organic nitrogen was recovered in the form of ammonium and nitrate ions during the irradiation process.     

Synthesis and Properties of Barium Dihydrogen 1-Hydroxyethane-1,1-diphosphonate Dihydrate

The only compound that crystallizes from aqueous solutions containing 1-hydroxyethane-1,1-di-phosphonic acid (H₄L) and Ba^{2 +} in molar ratios from 3 : 1 to 1 : 3 is BaH₂L·2H₂O. The product was characterized by powder X-ray diffraction, IR spectroscopy, and thermal analysis. The solubility of the compound in water (2.67 mM at 25°C) increases with temperature and with decreasing pH. No double salts M₂ ^IBa(H₂L)₂·nH₂O crystallize from aqueous solutions.     

Equilibres d'ionisation et photoréduction du vanadium(V) dans l'acide sulfurique concentré

By spectrophotometry of dilute solutions of V₂O₅ in concentrated sulfuric acid V^V? H₂SO₄ complexes are shown to convert slowly to V^IV monomers. Spectral, kinetic and equilibrium studies on these solutions suggest that this conversion involves a photoreduction of V^V to V^IV dimeric species.     

Copper and Nickel Removal from Aqueous Solutions Using New Chelating Poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid] Hydrogels

New poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid], poly [AAm/NVP/HECA], chelating hydrogels with different composition of HECA monomer have been prepared via free radical solution polymerization using N,N‐methylene bisacrylamide as a crosslinker. The hydrogels obtained were loaded with metal ions and characterized by FT‐IR spectroscopy, Scanning Electron Microscope (SEM) and Thermogravimatric analysis (TGA). The removal of Cu²⁺ and Ni²⁺ from aqueous solutions by the hydrogel was examined by a batch equilibrium method. The influence of treatment time, pH, initial concentration of the metal ions and HECA content in the feed compositions on the amount of adsorbed metal ions was studied. Swelling of the hydrogel was also carried out in distilled water and metal ion solutions. The removal of the metal ions followed the following order: Ni²⁺>Cu²⁺. The amount of metal ions removed increased with increasing HECA content in the feed composition, treatment time, pH of the medium and initial concentration of metal ions. The desorption of metal ions were carried out using 1 N HCl and 0.5 N H₂SO₄. The poly[AAm/NVP/HECA] hydrogels could be used many times without significantly decreasing their adsorption capacity.     

Stopped-flow study of H+ induced CO2 release from a non-peptide analogue of decarboxylase-substrate mimicking cis-[Cr(C2O4)(AaraNH2)(O2CO)]−

A stopped-flow method was used to investigate the kinetics of the acid hydrolysis of a newly synthesised coordination ion of the cis-[Cr(C₂O₄)(AaraNH₂)(O₂CO)]⁻ type, where AaraNH₂ stands for methyl 3-amino-2,3-dideoxy-α -d-arabino-hexapyranoside, over a range of hydrogen ion concentrations 0.01 < [H⁺] < 2.7 M and temperatures 5 < T < 25°C. Initiated by perchloric acid (HClO₄), the hydrolysis (decarboxylation) of the chromium(III) ion complexed with a bicoordinately linked carbonate ligand turned out to be a two-step process. The kinetic parameters k ₁, k ₂ were determined of both steps of the hydrolysis of the cis-[Cr(C₂O₄)(AaraNH₂)(O₂CO)]⁻ ion, as was the equilibrium constant K of the protonation of this ion, which precedes the actual two-step hydrolysis. From an analysis of the values of the constants obtained, a mechanism is proposed for the acid hydrolysis of the cis-[Cr(C₂O₄)(AaraNH₂)(O₂CO)]⁻ coordination ion.     

Kinetische und Gleichgewichtsuntersuchungen zur Aquotisierung und Halogenid-Anation an Halogeno-Aquo-Komplexen von Osmium(IV)

Kinetic and Equilibrium Studies on Aquation and Halide-Anation of Osmium(IV)- Halogeno-Aquo Complexes Complexes of type [OsI₅X]^2? (X = Cl, Br, I) undergo hydrolysis in acidic, aqueous solutions already at room temperature according to [OsI₅X]^2? + H₂O ? [OsI₅(H₂O)]^? + X^?. Rate constants of aquation and anation reactions as well as equilibrium constants are determined by spectrophotometrical measurements. The kinetic and equilibrium experimental results are giving similar thermodynamic data. Kinetic stability increases from I over Br to Cl whereas the thermodynamic stability decreases in the same order. The monoaquo complex is less stable than the hexahalo complexes by 2 kcal/mol, and is present as an intermediate product in the halogen exchange reactions carried out in dilute solutions.